Bicycles:
Lie on your mat with your back to the floor. Put your hands behind your head, but do not interlock the fingers. Lift your legs hip height and raise your head. Bring one leg in and twist toward that leg and then alternate and twist toward the other leg. Go as fast or slow as is comfortable to you without compromising your form. Try to do a set of 50. This is a great oblique exercise.
Tricep Push-ups:
Get into a push-up position with your back straight and your butt in alignment with your body. These are different than standard push-ups because your hands need to be shoulder distance apart with your arms touching your sides. Lower as low as you can to the floor and push-up. Try do 10 and work yourself up to more sets and repetitions. These are an excellent way to challenge your triceps.